Sorry to come in late but have been rather busy doing other things with my father's Monmouthshire links. Have you considered Penrhys cemetery (there used to be a Penrhys transcription on the Web). Dependent upon where she lived (in the Rhondda, I assume) she could have been buried in Treorchy, Penrhys, Ferndale (I think there was a cemetery there) Gilfach or Trealaw as well as the crematorium at Glyntaff. I know that my wife's grandmother who spent most of her life in Llwynypia was buried at Gilfach because of family links.
Ray Lewis (Western Australia)